There are numerous conventional pressure switches which utilize bolts and latches for applying pressure, or spring pressure configurations. Such conventional switches require adjustments in order to provide the desired amount of pressure at the contacts. Another disadvantage of conventional switches is the failure to provide a low pressure state before the switch is opened, or before the switch is closed, such that the pressure at the contact causes wear and stiffness during operation.
Conventional pressure switches often form unreliable electrical connections at the contacts when spring contacts are used. Furthermore, problems with contact sticking occur at elevated temperatures. Current induced thermal expansion of copper blades and terminals increases contact pressure in high rate spring pressure designs and may prevent the switch from opening if not carefully adjusted.
A further drawback of conventional switches is poor resistance to contact welding on fault closings.
Therefore, a reliable pressure switch which overcomes the above problems would be of great advantage in the electrical pressure switch industry.